A physical quantity sensor detects a physical quantity on the basis of a capacitance of a capacitor between a fixed electrode and a movable electrode. The sensor is, for example, disclosed in Japanese Patent Application Publication No. H05-304303 (i.e., U.S. Pat. No. 6,227,049). The sensor is used, for example an acceleration sensor.
In the above prior art, multiple sensors are necessitated to detect the acceleration in a wide range, i.e., to have a wide detection range. Therefore, a total size (i.e., total dimensions) of the multiple sensors becomes larger.
Further, another sensor is disclosed for example in Japanese Patent No. 2773495 (i.e., U.S. Pat. No. 5,441,300) and Japanese Patent Application Publication No. H10-282136. This sensor is a capacitance type acceleration sensor, and detects the acceleration on the basis of a capacitance change of a capacitor. The sensor has a certain relationship (i.e., output characteristics) between a capacitance change and the acceleration. It is required to have an excellent linearity of the relationship. However, the linearity of the relationship in the sensor is low. Specifically, the output of the sensor in accordance with the displacement of the movable electrode deviates from a predetermined line rapidly so that the sensor has a small detection range for detecting the acceleration. To secure the linearity in the detection range, the sensor has a spring-mass system. Therefore, it is difficult to secure the wide dynamic range of the acceleration. If the sensor is set to have the wide dynamic range, the sensitivity of the sensor becomes small. That is because the displacement of the movable electrode becomes small in a low acceleration range. Thus, the wide dynamic range and the high sensitivity in the sensor are incompatible. Therefore, it is required to manufacture two types of the sensors, which are the sensor having a low acceleration detection range and the sensor having a high acceleration detection range. Therefore, it is difficult to minimize the sensor.